Hi @hamodi1983,
I’m sorry to hear that you’re having issues with email delivery.
As different ISPs and email service providers use different factors as metrics to filter spam or block emails, some email addresses would receive the notification email, while some do not. The best way that we know to improve email deliverability would be to use an SMTP plugin to configure the website to send authenticated emails.
If your notification settings are correct, the issue is likely because the emails sent from WordPress are not authenticated (unlike emails sent directly from dedicated email service providers). As a result, they are likely to be filtered by the receiving mail server.
To resolve email delivery issues like this, you can configure an SMTP plugin on your site so that emails are sent as authenticated. We have an article with a list of recommended SMTP options and links to their setup tutorials.
I hope this helps ??